1. Field of the Invention
This invention relates to portable light units, such as safety inspection lights or "trouble" lights, and especially to the type of portable light unit that utilizes a fluorescent lamp rather than an incandescent bulb. More particularly, the invention relates to an improvement in portable fluorescent light units to facilitate the mounting of the lamp within the unit.
2. Description of the Prior Art
Portable fluorescent light units have many advantages compared with other types of "trouble" lights. Such portable fluorescent light units are often used to particular advantage in garages where automobile service is performed, as well as in other unlighted areas, such as attics, that are used infrequently. Prior units of this type generally utilize a tubular transparent plastic housing of fairly sturdy construction in which a fluorescent lamp, such as a 15-watt, 17-inch lamp is mounted along with the necessary sockets and a switch associated with the electrical circuitry. A ballast is provided on the power cord, and the cord is usually of sufficient length to enable the light to be carried around a relatively large area.
Typical prior art constructions of these light units are shown in U.S. Pat. No. 3,136,489 issued to Oharenco, U.S. Pat. No. 3,140,045 issued to Oharenco, and U.S. Pat. No. 3,242,331 issued to Behringer.
One difficulty encountered in the assembly of this type of light unit concerns the attachment of the fluorescent lamp sockets to the transparent tubular plastic housing. The lamp is usually held within the housing by a pair of sockets, one socket attached to each end of the lamp, with the sockets being mounted on a support bracket which is attached to the housing. The lamp has pins at each end which are mounted in and engage the sockets, the sockets having internal means for making a point contact with the pins to provide an electrical connection. In the assembly of the light unit it is necessary to attach the sockets to the brackets and pull the wires which extend from the sockets through openings in the brackets. The wires from each of the sockets must then be spliced together and spliced to the wires extending from the cord. These multiple splices add to the cost of construction of the lamps and present potential safety hazards since each splice must be made cleanly, and carefully, and must be safely taped or covered with a suitable splice closure or "wire nut". In addition, it is preferable to enclose any splice within an insulating area to prevent the problem of inadvertent current flow or shocks. The splicing procedure requires additional time in the assembly of the lamp and must be done carefully to avoid any problems of shock or inadvertent current flow resulting from the splice connection.
Another difficulty encountered in the construction and assembly of these light units is in providing a means for holding the fluorescent lamp snugly between the sockets and at the same time accommodating thermal expansion and contraction of the housing to which the socket supports are mounted. This thermal expansion is often the result of the heat generated by the lamp and by environmental temperature variations to which the light unit is subjected. One solution to the problem of thermal expansion is shown in U.S. Pat. No. 4,092,706, issued to the present inventor, in which each of the sockets is mounted on a special socket support which is capable of bending to accommodate thermal expansion. While this design has been shown to be completely suitable for the accommodation of thermal expansion, the socket supports are generally formed of a sheet metal material and therefore do not provide additional insulating capabilities.
Further difficulties result from the contact made by the sockets. These sockets generally provide only a small area of electrical connection between the contact with the socket and the pins extending from the fluorescent lamp. These sockets are designed primarily for stationary applications, such as mounted fluorescent fixtures, and do not provide a reliable electrical connection when used in a portable fluorescent light unit. Furthermore, the point contact for the electrical connection also serves as a mechanical means for securing the fluorescent lamp to the socket. While this securing means may be suitable for stationary applications, it is inadequate in a portable light unit which is subject to rough and sometimes abusive treatment, particularly where the point contact occurs midway along the length of the pin. This holding arrangement may result in bending of the pin or possible breakage of the hermetic seal between the pin and fluorescent lamp when subjected to mechanical shock or vibration.